Stereoscopic display method and apparatus

ABSTRACT

A stereoscopic display apparatus discriminates image signals for the left and right eyes by comparing the received image signals, and displays an image without adding special signals for discriminating the left and right eyes. A mechanical connection between an image pickup and an image display is not needed to properly distinguish left and right eye images.

BACKGROUND OF THE INVENTION

The present invention relates to a stereoscopic display method andapparatus such as a stereoscopic television system, which can achieve astereoscopic view on the basis of two, right and left image signalshaving a parallax.

In general, a stereoscopic display apparatus achieves a stereoscopicview by displaying image signals for the right and left eyes on displayunits for the right and left eyes, respectively.

In this case, a reproduction apparatus (display apparatus side) mustdiscriminate the image signals for the right and left eyes from eachother. For this purpose, a conventional apparatus adopts a method ofadding a discrimination pulse to one image signal or changing the numberof cycles of a color burst signal in one image signal on the imagepickup device side.

However, in the conventional stereoscopic display apparatus, the imagepickup device requires a circuit for adding a discrimination signal or acircuit for changing the number of cycles of the color burst signal,while the reproduction apparatus requires a circuit for extracting theadded discrimination signal or a circuit for detecting the number ofcycles of the color burst signal, resulting in a complicated systemarrangement.

As for a stereoscopic television system, a standard such as CCIR or thelike is not determined yet. For this reason, even when a certain systemadds a discrimination signal, the added signal cannot often bediscriminated by another system.

On the other hand, in place of adding such a discrimination signal, auser may connect, by himself or herself, image signals for the right andleft eyes to the display units for the right and left eyes,respectively. However, if the user erroneously recognizes the imagesignals for the right and left eyes, if he or she keeps watching animage displayed in such a state, his or her eyes suffer considerablefatigue.

SUMMARY OF THE INVENTION

The present invention has been made to solve the above-mentionedproblems, and has as its object to provide a stereoscopic displayapparatus which can discriminate image signals for the right and lefteyes and can normally display an image without adding any specialsignals for discriminating the image signals for the right and lefteyes.

The above-mentioned object is achieved by the following apparatus ormethod.

A stereoscopic display apparatus which receives two different imagesignals, and displays the two different image signals on display meanshaving portions for right and left eyes, respectively, comprises:right/left discrimination means for discriminating, based on acorrelation between the input two different image signals, which of thetwo different image signals corresponds to a signal for the right orleft eye; and switching means for switching image signals to be outputto the display means on the basis of a discrimination result of theright/left discrimination means.

A stereoscopic display method which receives two different imagesignals, and displays the two different image signals on display meansfor right and left eyes, respectively, comprises: a right/leftdiscrimination step of discriminating, based on a correlation betweenthe input two different image signals, which of the two different imagesignals corresponds to a signal for the right or left eye; and aswitching step of switching image signals to be output to the displaymeans on the basis of a discrimination result of the right/leftdiscrimination step.

Other features and advantages of the present invention will be apparentfrom the following description taken in conjunction with theaccompanying drawings, in which like reference characters designate thesame or similar parts throughout the figures thereof.

BRIEF DESCRIPTION OF THE DRAWINGS

The accompanying drawings, which are incorporated in and constitute apart of the specification, illustrate embodiment of the invention and,together with the description serve to explain the principles of theinvention.

FIG. 1 is a block diagram showing the arrangement of a stereoscopicdisplay apparatus according to the first embodiment of the presentinvention;

FIGS. 2A to 2C are explanatory views for explaining the right/leftdiscrimination operation executed by a right/left discrimination circuitshown in FIG. 1;

FIG. 3 is a graph showing the correlation calculation result by theright/left discrimination circuit shown in FIG. 1;

FIG. 4 is a circuit diagram showing the arrangement of a switchingcircuit shown in FIG. 1;

FIG. 5 is a block diagram showing the arrangement of a right/leftdiscrimination circuit used in a stereoscopic display apparatusaccording to the second embodiment of the present invention;

FIGS. 6A and 6B are explanatory views for explaining the right/leftdiscrimination operation executed by a right/left discrimination circuitshown in FIG. 5;

FIG. 7 is a graph showing the correlation calculation result by theright/left discrimination circuit shown in FIG. 5;

FIG. 8 is a block diagram showing the arrangement of a stereoscopicdisplay apparatus according to the third embodiment of the presentinvention; and

FIG. 9 is a flow chart for explaining the right/left discriminationoperation sequence of the third embodiment.

FIGS. 10A to 10C are views for explaining the operation of a displayapparatus according to the fourth embodiment of the present invention;

FIGS. 11A and 11B are views showing the correlation calculation resultin the display apparatus according to the fourth embodiment;

FIG. 12 is a block diagram showing the arrangement of a switchingcircuit in a display apparatus according to the fifth embodiment of thepresent invention; and

FIGS. 13A and 13B are views for explaining the operation of the displayapparatus according to the fifth embodiment.

DESCRIPTION OF THE PREFERRED EMBODIMENTS

Preferred embodiments of the present invention will be described indetail in accordance with the accompanying drawings.

(First Embodiment)

The first embodiment of the present invention will be described belowwith reference to FIGS. 1 to 4.

FIG. 1 is a schematic block diagram showing the arrangement of astereoscopic display apparatus according to this embodiment. Referringto FIG. 1, reference numerals 101 and 102 denote input terminals whichrespectively receive a composite video signal VIDEO1 as an image signalfor the right eye and a composite video signal VIDEO2 as an image signalfor the left eye. In this embodiment, the right and left composite videosignals VIDEO1 and VIDEO2 are synchronized with each other, and areinput in a state wherein they can be driven based on the same timingrelationship. A power supply voltage for operating this displayapparatus is supplied from a power supply circuit 125. When a switch inthe power supply circuit 125 is turned on, the power supply voltage issupplied to respective blocks via connection lines (not shown).

The input terminals 101 and 102 are respectively connected to YCseparation circuits 103 and 104 each for separating the video signalinto a luminance signal and a chrominance signal. The YC separationcircuit 103 and 104 are connected to a right/left discrimination circuit105 for discriminating whether or not the right and left video signalsare normally input, and a switching circuit 106 for outputting the rightand left video signals to appropriate blocks on the basis of thediscrimination result of the right/left discrimination circuit 105. Theright/left discrimination circuit 105 comprises a correlationcalculation unit 105a and a discrimination unit 105b. The input terminal101 is also connected to a synchronization separation circuit 107 forextracting a synchronization signal from the input video signal VIDEO.The synchronization separation circuit 107 is connected to theright/left discrimination circuit 105, decoder circuits 108 and 109 forthe image signals for the right and left eyes, and a timing generator110, and outputs a synchronization signal to these circuits.

The switching circuit 106 is connected to the decoder circuits 108 and109 for the right and left eyes, and outputs the image signals for theright and left eyes to the decoder circuits 108 and 109 for the rightand left eyes, respectively.

The decoder circuit 108 is connected to a liquid crystal panel 115 viaan RGB matrix circuit 112, an inverse γ circuit 113, and an analogdriver 114. The analog driver 114 comprises a signal inversion circuitfor inversion-driving the liquid crystal panel 115, an amplifier circuitfor amplifying an input signal to a signal amplitude required fordriving the liquid crystal panel 115, and a buffer circuit foroutputting the image signal for the right eye to the liquid crystalpanel 115. The analog driver 114 is connected to the timing generator110, and its operation timing is controlled. The timing generator 110generates timing signals for ON/OFF control of pixel transistors of theliquid crystal panel 115 and for transfer clocks of a shift register onthe basis of the synchronization signal separated and output from thesynchronization separation circuit 107 under the control of a systemcontroller 111. These timing signals are input to the analog driver 114,a digital driver 116 for driving the liquid crystal panel 115, abacklight 117 for illuminating the liquid crystal panel 115 from therear surface side, and a backlight turn-on circuit 118 for driving thebacklight 117.

The decoder circuit 109, an RGB matrix circuit 119, an inverse γ circuit120, an analog driver 121, a liquid crystal panel 122, a digital driver123, and a backlight 124 as the arrangement for processing the imagesignal for the left eye are respectively connected in the same manner asthe above-mentioned decoder circuit 108, RGB matrix circuit 112, inverseγ circuit 113, analog driver 114, liquid crystal panel 115, digitaldriver 116, and backlight 117. The analog driver 121 and the digitaldriver 123 display an image for the left eye on the liquid crystal panel122 in synchronism with the analog driver 114 and the digital driver 116for the right eye on the basis of the operation timing signals outputfrom the timing generator 110.

In the above-mentioned arrangement, the video signal VIDEO1 input viathe input terminal 101 is separated into a luminance signal Yri and achrominance signal Cri by the YC separation circuit 103. The luminancesignal Yri is input to the right/left discrimination circuit 105 and theswitching circuit 106, and the chrominance signal Cri is input to theswitching circuit 106. On the other hand, the video signal VIDEO2 inputvia the input terminal 102 is separated into a luminance signal Yli anda chrominance signal Cli by the YC separation circuit 104. The luminancesignal Yli is input to the right/left discrimination circuit 105 and theswitching circuit 106, and the chrominance signal Cli is input to theswitching circuit 106.

The synchronization signal extracted by the synchronization separationcircuit 107 is input to the right/left discrimination circuit 105together with the luminance signals Yri and Yli. The right/leftdiscrimination circuit 105 extracts signal components corresponding to ascanning line position used for discrimination from the right and leftluminance signals Yri and Yli by a method to be described later on thebasis of the synchronization signal input from the synchronizationseparation circuit 107. Then, the circuit 105 discriminates whether ornot the right and left video signals are normally input, and outputs adiscrimination signal DET of HIGH level if it is determined that theright and left video signals are normally input; otherwise, it outputs adiscrimination signal DET of LOW level. The discrimination signal DET isinput to the switching circuit 106 together with the luminance signalsYri and Yli and the chrominance signals Cri and Cli. The right/leftdiscrimination circuit 105 is also connected to the system controller111, and the level of the discrimination signal DET is checked.

The operation of the right/left discrimination circuit 105 will bedescribed below with reference to FIGS. 2A to 3.

FIG. 2A is a view for explaining the relationship between an object andthe fields of view of photographing lenses in an image pickup device forobtaining a stereoscopic image to be displayed on the display apparatus.Referring to FIG. 2A, reference numeral 201 denotes an object; 202 and203, photographing lenses for the right and left eyes; and 204 and 205,image pickup elements for the right and left eyes. The field of view ofthe photographing lens 202 for the right eye is indicated by solid lines206 and 207, and the field of view of the photographing lens 203 for theleft eye is indicated by solid lines 208 and 209. Broken lines 210 and211 respectively represent the optical axes of the right and leftphotographing lenses, and the two optical axes 210 and 211 are set to beparallel to each other.

FIG. 2B is a view showing images formed on the image pickup elements 204and 205. Referring to FIG. 2B, reference numerals 212 and 213 denotefield frames of the photographing lenses for the right and left eyes,respectively; and 201r and 201l, images of the object 201 formed on theright and left image pickup elements 204 and 205, respectively.

FIG. 2C shows the signal waveforms of a scanning line corresponding to aposition indicated by an alternate long and short dashed line 214 inFIG. 2B. Signal waveforms 215 and 216 respectively correspond to onescanning line used for discrimination of the above-mentioned luminancesignals Yri and Yli.

As can be seen from FIGS. 2B and 2C, when the optical axes 210 and 211of the photographing lenses are set to be parallel to each other, theposition of the object image 201r in the field frame 212 is near theleft end, and the position of the object image 201l in the field frame213 is near the right end. In order to detect a relative positionalrelationship, in the right-and-left direction, of the object on thebasis of the signal waveforms shown in FIG. 2C, the correlationcalculation unit 105a performs a correlation calculation between thesignal waveforms 215 and 216.

More specifically, if the signal waveform 215 in the field frame 212 isrepresented by Xr(t) and the signal waveform 216 in the field frame 213is represented by Xl (t), a correlation calculation result (correlationparameter) Clr(T) is given by: ##EQU1## note that the integral range isone horizontal scanning period T.

When the correlation calculation is executed based on equation (1), theresult shown in FIG. 3 is obtained. More specifically, when thecorrelation calculation is executed based on image data Xr(t) for theright eye, a value τα corresponding to a peak value of the calculationresult Clr(T) is a positive value.

On the other hand, when the image signals for the right and left eyesare input to the wrong sides, since the value τα corresponding to a peakvalue is a negative value, whether or not the right and left videosignals are normally input can be discriminated by checking the polarityof the value τα.

The switching circuit 106 will be described below with reference to FIG.4. FIG. 4 is a circuit diagram showing the arrangement of the switchingcircuit 106. The switching circuit 106 has analog switches 401 to 404for switching an input signal. The analog switches 401 to 404 areswitching-controlled by a single control signal DET. More specifically,output terminals 401a to 404a are connected to h terminals 401b to 404bwhen the control signal DET is at HIGH level, and are connected to lterminals 401c to 404c when the control signal DET is at LOW level. Theoutput terminals 401a and 402a are connected to the decoder circuit 108for the right eye, and the output terminals 403a and 404a are connectedto the decoder circuit 109 for the left eye.

As described above, the switching circuit 106 receives the luminancesignals Yri and Yli, the chrominance signals Cri and Cli, and thediscrimination signal DET output from the right/left discriminationcircuit 105. The luminance signal Yri input from the YC separationcircuit 103 for the image signal for the right eye is input to the hterminal 401b of the analog switch 401 and the l terminal 403c of theanalog switch 403, and the chrominance signal Cri is input to the hterminal 402b of the analog switch 402 and the l terminal 404c of theanalog switch 404. On the other hand, the luminance signal Yli inputfrom the YC separation circuit 104 for the image signal for the left eyeis input to the l terminal 401c of the analog switch 401 and the hterminal 403b of the analog switch 403, and the chrominance signal Cliis input to the l terminal 402c of the analog switch 402 and the hterminal 404b of the analog switch 404.

In this arrangement, when the video signal VIDEO1 for the right eye isinput to the input terminal 101, and the video signal VIDEO2 for theleft eye is input to the input terminal 102, the discrimination signalDET output from the right/left discrimination circuit 105 changes toHIGH level. At this time, since all the output terminals 401a to 404a ofthe analog switches 401 to 404 are connected to the h terminals 401b to404b, output signals Yro, Cro, Ylo, and Clo from the output terminals401a to 404a are respectively equal to the input signals Yri, Cri, Yli,and Cli. On the other hand, when the video signal VIDEO2 for the lefteye, which is to be input to the input terminal 102, is input to theinput terminal 101, and the video signal VIDEO1 for the right eye, whichis to be input to the input terminal 101, is input to the input terminal102, since the discrimination signal DET output from the right/leftdiscrimination circuit 106 changes to LOW level, all the outputterminals 401a to 404a of the analog switches 401 to 404 are connectedto the input terminals 401c to 404c, and the output signals Yro, Cro,Ylo, and Clo from the output terminals 401a to 404a are respectivelyequal to the input signals Yli, Cli, Yri, and Cri. Therefore, even whenthe video signals for the right and left eyes are input to the wrongsides, the image signal for the right eye can be normally input to thedecoder circuit 108 for the right eye, and the image signal for the lefteye can be normally in put to the decoder circuit 109 for the left eye.

Referring back to FIG. 1, the chrominance signal Cro of the video signalfor the right eye, which is input to the decoder circuit 108 for theright eye by the above-mentioned method, is converted into basebandcolor difference signals R-Yr and B-Yr, and the converted signals areinput to the RGB matrix circuit 112 in synchronism with thesynchronization signal. On the other hand, the luminance signal Yro isoutput as a signal Yr without being subjected to any special processing.The RGB matrix circuit 112 respectively converts the color differencesignals R-Yr and B-Yr, and the luminance signal Yr into R, G, and Bsignals Rr, Gr, and Br, and the R, G, and B signals are input to theanalog driver 114 after they are subjected to gradation correction inthe inverse γ circuit 113. The analog driver 114 inverts and switchesthe R, G, and B signals Rr, Gr, and Br in accordance with an inputinversion control signal from the timing generator 110, amplifies thesesignals, and outputs analog image signals to the liquid crystal panel115 for the right eye.

The liquid crystal panel 115 displays the input analog image signalsunder the driving control of the digital driver 116. At this time, thesystem controller 111 monitors the output state of the discriminationsignal DET output from the right/left discrimination circuit 105. Whenthe controller 111 determines that the output state of thediscrimination signal is not inverted for a predetermined period oftime, i.e., stabilized, it controls the timing generator 110 to turn onthe backlight 117.

On the other hand, the decoder circuit 109, RGB matrix circuit 119,inverse y circuit 120, analog driver 121, liquid crystal panel 122,digital driver 123, and backlight 124 constitute the arrangement forprocessing the image signal for the left eye, and operate in the samemanner as the above-mentioned decoder circuit 108, RGB matrix circuit112, inverse circuit 113, analog driver 114, liquid crystal panel 115,digital driver 116, and backlight 117. Thus, a detailed descriptionthereof will be omitted.

As described above, according to this embodiment, even when the videosignals for the right and left eyes are input to the wrong sides, theright/left discrimination circuit 105 can discriminate such a state, andthe switching circuit 106 can switch circuits, so that the image signalfor the right eye can be normally input to the decoder circuit 108 forthe right eye, and the image signal for the left eye can be normallyinput to the decoder circuit 109 for the left eye.

(Second Embodiment)

The second embodiment of the present invention will be described belowwith reference to FIGS. 5 to 7.

The display apparatus according to this embodiment adopts a right/leftdiscrimination circuit 105' shown in FIG. 5 in place of the right/leftdiscrimination circuit 105 shown in FIG. 1 in the first embodimentdescribed above. The right/left discrimination circuit 105' comprisesfield memories 501 and 502, a region setting unit 503, a correlationcalculation unit 504, and a discrimination unit 505. Note that otherarrangements are the same as those of the display apparatus shown inFIG. 1 in the first embodiment, and will be described while quoting FIG.1.

A luminance signal Yri separated from a video signal VIDEO1 by the YCseparation circuit 103 is input to the field memory 501, and a luminancesignal Yli separated from a video signal VIDEO2 by the YC separationcircuit 104 is input to the field memory 502. The read/write control ofthe field memories 501 and 502 is executed by the system controller 111.A synchronization signal extracted by the synchronization separationcircuit 107 is input to the region setting unit 503.

The region setting unit 503 extracts only image data in a range, inwhich it is estimated that a principal object is present, from the rightand left image signals. In a normal photographing operation, since theprincipal object is normally located at the center of the frame, imagedata near the center of the frame are extracted from the luminancesignals Yri and Yli, as indicated by broken lines in FIG. 6B, and theextracted data are input to the correlation calculation unit 504.

The correlation calculation unit 504 executes a correlation calculationbetween the image signals for the right and left eyes in the same manneras in the first embodiment, and the discrimination unit 505discriminates, based on the correlation calculation result, whether ornot the right and left video signals are normally input. As a result ofdiscrimination, if the right and left video signals are normally input,a discrimination signal DET of HIGH level is output; otherwise, adiscrimination signal DET of LOW level is output.

The operation of the right/left discrimination circuit 105' will bedescribed below with reference to FIGS. 6A to 7. FIG. 6A is a view forexplaining objects and the fields of view of photographing lenses in animage pickup device for obtaining a stereoscopic image to be displayedon the stereoscopic display apparatus, and illustrates a state whereinobjects 601 and 602 are added to the state of FIG. 2A in the firstembodiment. FIG. 6B shows images formed on the image pickup elements 204and 205 in FIG. 6A. Referring to FIG. 6B, reference numerals 603 and 604denote field frames of the photographing lenses for the right and lefteyes, respectively; 601r and 601l, images of the object 601 formed onthe right and left image pickup elements 204 and 205, respectively; and602r and 602l, images of the object 602 formed on the right and leftimage pickup elements 204 and 205, respectively.

The region setting unit 503 sets regions indicated by broken lines 605and 606 in FIG. 6B in the field frames 603 and 604. When the correlationcalculation between two image data in these ranges is executed, acorrelation parameter Clr(τ) shown in FIG. 7 is obtained. As can be seenfrom FIG. 7, when there are a plurality of objects, a clear peak valuedoes not appear. However, as can be understood from a comparison betweenan area (integral value) Sa of a region a satisfying τ>0 indicated byhatching in FIG. 7, and an area (integral value) Sb of a region bsatisfying τ<0, Sa>Sb. Therefore, by comparing the areas Sa and Sb ofthe regions a and b, when Sa>Sb, it is determined that the right andleft image data are normally input, and when Sa<Sb, it is determinedthat the right and left image data are input to the wrong sides.

As described above, according to this embodiment, when there are aplurality of objects, the correlation calculation is performed for theentire data in a region where it is estimated that the objects arepresent, in place of the correlation calculation using image data forone scanning line. Therefore, background images in the field frames canbe removed, and right/left discrimination can be accurately per formedfor an object with a complicated shape.

(Third Embodiment)

The third embodiment of the present invention will be described belowwith reference to FIGS. 8 and 9.

FIG. 8 is a block diagram showing the arrangement of a display apparatusaccording to this embodiment. This display circuit comprises, as newcircuits, an input detection circuit 130 for detecting inputs of videosignals, a synchronization separation circuit 131 for extracting asynchronization signal from a video signal VIDEO2 for the left eye, anda timer 132 which is connected to the system controller 111 and measurestime from the input timing of the video signals. The input detectioncircuit 130 is connected to the synchronization separation circuits 107and 131, and receives synchronization signals separated from videosignals VIDEO1 and VIDEO2. Furthermore, the input detection circuit 130is connected to the right/left discrimination circuit 105 and the systemcontroller 111, and outputs an input detection signal to the right/leftdiscrimination circuit 105 and the system controller 111. The right/leftdiscrimination circuit 105 is not connected to the switching circuit106, and outputs a discrimination signal DET to the system controller111. The switching control of the switching circuit 106 is executed bythe system controller 111. Other arrangements are the same as those inFIG. 1 in the first embodiment, and the same reference numerals in FIG.8 denote the same parts as in FIG. 1.

A video signal VIDEO2 input via the input terminal 102 is input to thesynchronization separation circuit 131, and a synchronization signalextracted by the circuit 131 is input to the input detection circuit130. At the same time, a synchronization signal extracted, by thesynchronization separation circuit 107, from a video signal VIDEO1 inputvia the input terminal 101 is also input to the input detection circuit130. The input detection circuit 130 detects the input of the imagesignals by checking, e.g., the pulse intervals of the twosynchronization signals.

The right/left discrimination operation sequence executed in the displayapparatus with the above arrangement will be described below withreference to the flow chart shown in FIG. 9.

When the power switch of the power supply circuit 125 is turned on (stepS901), the input detection circuit 130 starts its operation (step S902).If it is detected that the video signals are input to both the inputterminals 101 and 102, the input detection circuit 130 outputs an inputdetection signal indicating the input of the video signals to the systemcontroller 111. Upon reception of the input detection signal, the systemcontroller 111 starts the timer 132 (step S903), and starts theoperation of the right/left discrimination circuit 105 (step S904).

The right/left discrimination circuit 105 repetitively performs theright/left discrimination operation by the above-mentioned method untila predetermined period of time elapses from the start of the timer, andoutputs the discrimination results to the system controller 111 (stepS905). The system controller 111 stores all the discrimination results(HIGH or LOW levels of the discrimination signals) input from theright/left discrimination circuit 105 before an elapse of thepredetermined period of time. After the elapse of the predeterminedperiod of time, the system controller 111 stops the timer 132 (stepS906), and compares the numbers of HIGH- and LOW-level signals of theobtained discrimination results (step S907).

In an initial state after power-ON, the output terminals 401a to 404a ofthe analog switches 401 to 404 in the switching circuit 106 areconnected to the h terminals 401b to 404b. If the system controller 111determines in step S907 that the number of HIGH-level discriminationsignals DET is larger than that of LOW-level discrimination signals DET,it maintains the switching circuit 106 in the initial state; otherwise,it switches the output terminals 401a to 404a to the l terminals 401c to404c (step S908). Upon completion of the operation of the switchingcircuit 106, the system controller 111 controls the timing generator 110to drive the backlight turn-on circuit 118 (step S909). In this state,the liquid crystal panels 115 and 122 are set in an image display state,and keep displaying an image until the power switch is turned on (stepS910).

As described above, according to this embodiment, since the right andleft signals are finally discriminated based on the majority rule afteran elapse of a predetermined period of time from the input of the rightand left video signals, the discrimination can be performed moreaccurately. Furthermore, the switching circuit is controlled inaccordance with the discrimination result, and is not switched once thediscrimination result is obtained. For this reason, the operation duringdisplay can be stabilized.

As described above, according to the stereoscopic display apparatus ofeach of the above embodiments of the present invention, in astereoscopic display apparatus which receives two different imagesignals, and displays the two different image signals on two displaymeans for the right and left eyes, respectively, the right/leftdiscrimination means discriminates, based on a correlation between theinput two different image signals, if each of the two different imagesignals corresponds to a signal for the right or left eye, and the imagesignals output to the two display means are switched on the basis of thediscrimination result. Therefore, the image signals for the right andleft eyes can be accurately discriminated and displayed without addingany special signal for discriminating the image signals for the rightand left eyes from each other.

According to the stereoscopic display apparatus of each of the aboveembodiments of the present invention, since the right/leftdiscrimination means discriminates, in a region set by the regionsetting means, if each of the two different image signals corresponds toa signal for the right or left eye, the right/left discrimination can beaccurately performed for an object with a complicated shape in additionto the above effect.

According to the stereoscopic display apparatus of each of the aboveembodiments of the present invention, the signal input discriminationmeans discriminates if the two different image signals are input. Theright/left discrimination means discriminates signals for the right andleft eyes a plurality of number of times for a predetermined period oftime from when the signal input discrimination means discriminates thatthe two different image signals are input, and determines the majorityof the discrimination results. Thereafter, the image signals areswitched by the switching means on the basis of the result correspondingto the majority. Therefore, whether or not image signals for the rightand left eyes are normally input can be discriminated more accurately.

According to the stereoscopic display apparatus of each of the aboveembodiments of the present invention, since the switching operation ofimage signals by the switching means is stopped after the elapse of thepredetermined period of time, the operation during display of thedisplay apparatus can be stabilized.

(Fourth Embodiment)

The fourth embodiment of the present invention will be described withreference to FIGS. 10A to 10C, 11A, and 11B. Note that the basicarrangement of a display apparatus of this embodiment is the same asthat of the first embodiment in FIG. 1, and the arrangement of aright/left discrimination circuit of the fourth embodiment is identicalto that in FIG. 5. The fourth embodiment will also be described withreference to FIGS. 1 and 5.

In the above-mentioned embodiments, the optical axes of the right andleft cameras are set to be parallel to each other. However, in thefourth embodiment, the optical axes of right and left cameras cross eachother at a given vergent angle.

FIG. 10A is a view showing a state in which spherical objects 1013,1001, and 1012 are vertically arranged on a table 1018, and optical axes1011 and 1010 of the left and right cameras are focused on the object1001. In this case, the images of the right and left cameras are shownin FIGS. 10B and 10C.

FIG. 10B shows discrimination regions 1016 and 1017 defined at locationswhere the objects are present as in the second embodiment. When acorrelation calculation is performed for these discrimination regions1016 and 1017 as in the second embodiment, a graph shown in FIG. 11A isobtained. In this case, since the optical axes 1011 and 1010 of the leftand right cameras are directed toward the objects, the correlationvalues are almost symmetrical about τ=0, unlike in FIG. 7. Theright/left discrimination operation cannot be performed by comparing aregion a with a region b.

FIG. 10C shows a state in which the discrimination regions 1016 and 1017are set below the central portion of the frame using a region settingunit 503 in FIG. 5. In general, within a photographing frame, when acamera faces toward a principal object, an object photographed in thelower portion of the frame is located in the left portion of the framein the left camera and in the right portion of the frame in the rightcamera because the object in the lower portion of the frame is locatedin front of the principal object. For this reason, correlation valuesobtained when the discrimination regions 1016 and 1017 are defined, asshown in FIG. 10C, are given as follows. The region a having a positiveT values has a larger area than the region b having a negative τ values,as shown in FIG. 11B. Therefore, the areas of the regions a and b arecompared with each other to allow right/left discrimination as in thesecond embodiment.

Note that the above description applies to a case in which an object isphotographed from a camera above the object. However, when an object isphotographed by a camera below the object, the discrimination regions1016 and 1017 are set above the central portion of the frame by theregion setting unit 503, and the following processing is performed toallow right/left discrimination, as a matter of course.

According to this embodiment, right/left discrimination can be performedeven if the optical axes 1011 and 1010 of the left and right cameras arenot set to be parallel to each other.

(Fifth Embodiment)

The fifth embodiment of the present invention will be described withreference to FIGS. 12, 13A, and 13B. The basic arrangement of a displayapparatus according to this embodiment is the same as that of the firstembodiment in FIG. 1, and the fifth embodiment will also be describedwith reference to FIGS. 1 and 5. The fifth embodiment is different fromthe first embodiment in the arrangement of a right/left discriminationcircuit.

FIG. 12 is a block diagram showing the arrangement of a right/leftdiscrimination circuit 6b in the display apparatus according to thisembodiment. Referring to FIG. 12, a signal input to the right/leftdiscrimination circuit 6b is luminance signals Yri and Yli, and asynchronization signal. A signal output from the right/leftdiscrimination circuit 6b is also a discrimination signal DET. Unlike inthe first embodiment, the fifth embodiment additionally includes firstand second field memories 1201 and 1202, an object extraction circuit1203, a region discrimination circuit 1204, a size comparison circuit1205, and a discrimination circuit 1206.

The right and left luminance signals Yri and Yli are temporarily storedin the first and second field memories 1201 and 1202. Data exchange isperformed between the field memories 1201 and 1202 and the objectextraction circuit 1203 to extract an object within the frame. Theregion discrimination circuit 1204 discriminates whether the extractedobject is located in the left or right half of the frame. In addition,the sizes of the right and left input images of the identical object arecompared by the size comparison circuit 1205. Right/left discriminationis then performed by the discrimination circuit 1206 on the basis of thecomparison result.

This discrimination method is shown in FIGS. 13A and 13B. FIG. 13A showsa state in which two objects 1312 and 1313 are photographed by left andright cameras whose optical axes 1311 and 1310 have a given vergentangle. In this case, the photographing frames are shown in FIG. 13B. Inthis embodiment, object portions of the images shown in FIG. 13B areextracted by the object extraction circuit 1203 in accordance with acontour extraction method or the like, and the right and leftcorresponding object images are specified in accordance with acorrelation calculation or the like. In this case, an image 1312lcorresponds to an image 1312r, and an image 1313l corresponds to animage 1313r. The region discrimination circuit 1204 then discriminateswhether each of the corresponding objects is located in the right orleft half of the frame. This can be easily -known in accordance withaddresses of data in the first and second field memories 1201 and 1202.In addition, the sizes of the objects are compared with each other bythe size comparison circuit 1205. This size comparison is performed asfollows. Correlation calculations are performed while the imagemagnification is changed step by step. An image magnificationcorresponding to the maximum correlation value is discriminated, andsize comparison is performed at this image magnification.

Note that although the region discrimination circuit discriminateswhether each of the corresponding objects is located in the right orleft half of the frame, the area of a region to the left of the centerof the object is compared with the area of a region to the right of thecenter of the object, and a larger region is selected, as a matter ofcourse. In the object extraction circuit 1202, the objects are subjectedto segmentation in accordance with contour extraction to performmatching processing. Alternatively, the object extraction circuit 1202may determine the image magnification described with reference to thesize comparison circuit 1205, and matching processing between the rightand left images may be performed at the determined image magnification.This matching processing is performed after the objects of the right andleft images are scaled.

In the processing of the size comparison circuit 1205 and thediscrimination circuit 1206, scaling data of the objects of the matchedright and left images are equivalent to the size comparison resultbetween the objects. Therefore, right/left discrimination can beperformed on the basis of the scaling data for the objects.

As can be apparent from FIG. 11B, the image of the right camera islarger than that of the left camera in the right half of the frame.However, the image of the left camera is larger than that of the rightcamera in the left half of the frame. For this reason, the regiondiscrimination circuit 1204 in FIG. 12 discriminates that a larger imageof the object 1312 discriminated to be located on the right side isdiscriminated as the image of the right camera. To the contrary, alarger image of the object 1313 discriminated to be located on the leftside is discriminated as the image of the left camera.

FIGS. 12, 13A, and 13B have exemplified that the number of objects istwo. However, when the number of corresponding objects is increased,precision of right/left discrimination can be improved.

According to this embodiment, right/left discrimination can be performedwhen the optical axes of the right and left cameras are not set to beparallel to each other as in the first and second embodiments or when anappropriate object is not photographed in the lower portion of the frameas in the fourth embodiment.

As has been described above, in the display apparatus of the presentinvention, right and left images can be correctly connected with asimple arrangement without adding a circuit for adding a right/leftdiscrimination signal to the image pickup device.

As many apparently widely different embodiments of the present inventioncan be made without departing from the spirit and scope thereof, it isto be understood that the invention is not limited to the specificembodiments thereof except as defined in the appended claims.

What is claimed is:
 1. A stereoscopic display apparatus which receivestwo different image signals, and displays the two different imagesignals, comprising:display means for stereoscopic display havingportions for right and left eyes; right/left determination means fordiscriminating, based on a correlation between the input two differentimage signals, determining which of the two received different imagesignals corresponds to a signal for the right or left eye by comparingthe two different image signals to each other and for generating adetermination result; and switching means for switching image signals tobe output to the display means based on the determination result of saidright/left determination means.
 2. The apparatus according to claim 1,wherein said right/left determination means comprises correlation valuecalculation means for calculating a correlation value representing thecorrelation between image data of the two different image signals, anddetermines based on the calculated correlation values which of the twodifferent image signals corresponds to a signal for the right or lefteye.
 3. The apparatus according to claim 2, wherein said right/leftdetermination means comprises region setting means for setting a regionfor determining which of the two different image signals corresponds toa signal for the right or left eye.
 4. The apparatus according to claim2, further comprising:signal input discrimination means fordiscriminating whether or not the two different image signals are input,and wherein said right/left determination means determines the signalsfor the right and left eyes a plurality of times for a predeterminedperiod of time from when said signal input discrimination meansdiscriminates that the two different image signals are input, anddetermines a majority result based on the determinations, and saidswitching means switches the image signals on the basis of the majorityresult.
 5. A stereoscopic display method which receives two differentimage signals, and displays the two different image signals on displaymeans for stereoscopic display for right and left eyes, respectively,comprising:a right/left determination step of determining which of thetwo received different image signals corresponds to a signal for theright or left eye by comparing the two different image signals to eachother and for generating a determination result; a switching step ofswitching the two different image signals to be output to the displaymeans based on the determination result of said right/left determinationstep; and a displaying step of displaying the two different imagesignals on the display means.
 6. The method according to claim 5,wherein said right/left determination step comprises correlation valuecalculation step of calculating a correlation value representing thecorrelation between image data of the two different image signals, anddetermines, based on the calculated correlation value, which of the twodifferent image signals corresponds to a signal for the right or lefteye.
 7. The method according to claim 6, wherein said right/leftdetermination step comprises a region setting step of setting a regionfor determining which of the two different image signals corresponds toa signal for the right or left eye.
 8. The method according to claim 6,further comprising:a signal input discrimination step of discriminatingwhether or not the two different image signals are input, and whereinsaid right/left determination step determines the signals for the rightand left eyes a plurality of times for a predetermined period of timefrom when said signal input discrimination step discriminates that thetwo different image signals are input, and determines a majority resultbased on the determinations, and said switching step switches the imagesignals on the basis of the majority result.
 9. A stereoscopic displayapparatus which receives two different image signals, and displays thetwo different image signals, comprising:display means for stereoscopicdisplay having portions for right and left eyes; right/leftdetermination means for determining which of the two received differentimage signals corresponds to a signal for the right or left eye bycomparing the two different image signals to each other and forgenerating a determination result; and switching means for providing thetwo received different image signals to proper output terminals for theright eye and for the left eye based on the determination result of saidright/left determination means.